Mr Dunn’s mother Charlotte Charles told the paper on Saturday: “Things are now beginning to fall into place.

“In our deepest, darkest hour, we could not understand how anybody could just get on a plane after such a catastrophic crash and leave a devastated family behind.

“We have also found it impossible to figure out why the US administration has behaved in the lawless way it has in harbouring Anne Sacoolas. But no one is above the law.

“Whether or not you are a CIA officer, a diplomat or anyone else, the Vienna Convention states that you must abide by and respect the rules and regulations of the host country.

“Her leaving, and the US government protecting her and refusing the extradition request, is nothing short of a disgrace and we will not stand for it.

“Whether she is CIA or not, she must come back and I will not rest until she does.”

The UK previously issued an extradition request for Mrs Sacoolas to the US, but it was refused by Secretary of State Mike Pompeo.

Lawyers acting for the Dunn family have said it is the first time in the 100-year history of the extradition treaty that such a request has been turned down by the US.

Mrs Charles has previously said she felt Prime Minister Boris Johnson needed to "use his power" to put the pressure on President Donald Trump and Mr Pompeo to send the suspect back to the UK.

She said: "The fact that he has come out and said that is obviously a good thing but we hope that he can follow this up with actions now.

"He needs to use his power, because he's the only person with the power to tell Trump and Pompeo that she needs to come back.

"It feels good that he's on the same page as us and this is certainly a step in the right direction."

Asked what her message to the Prime Minister would be, Mrs Charles said: "Make the country proud of you. There are a lot of people out there who don't necessarily have faith in this Government and this is a chance for him to restore a bit of that faith.

"It's certainly another step forward but until I see action, they are not empty words, but they are words that need action behind them to show us that they are 100 per cent going to stand up for us."